The use of fibrous materials as a reinforcing means within a batch or mix of settable or hardenable material is well known. In ancient times straw fibers were utilized to reinforce sunbaked bricks. More recently, asbestos fibers have been used to reinforce portland cement mix, and glass fibers to reinforce plastics. However, it is only in the very recent past that fibers have been used to reinforce concrete and that fibrous concrete has become a practical reality.
Fibrous concrete comprises an ordinary concrete to which short, small diameter fibers have been added. Such fibers as asbestos, glass, plastics and steel have been employed in this manner, and the compressive strength of the resultant concrete may be one and one-half times greater than that of ordinary concrete, while the flexural strength may be increased by a factor of as much as two or two and one half.
The properties of fibrous concrete vary with such parameters as cement content, aggregate size, fiber geometry, the amount of fiber and the evenness of distribution of the fiber content. While the strength of fibrous concrete generally increases with increasing fiber content, the workability of the mix is severely impaired if the fiber content exceeds two percent, generally, of the volume of the mix. Thus, it is apparent that optimized fiber concrete characteristics necessitate a controlled and even flow of the fibers to the mix.
Steel fibers, the more common in use in fibrous concrete, typically are one-half to one and one-half inches in length and one to two hundredths of an inch in diameter, and they are commonly purchased in forty-pound boxes, the contents of which are manually separated and added to a cement mix, a time-consuming and expensive procedure, wholly lacking in uniformity of mix.
The prior art is replete with various forms of rotary drum devices for classifying or screening articles of all types. That is to say, the prior art abounds with rotary drum devices for separating two or more ingredients of an agglomeration where the several ingredients have different physical characteristics, such as size or shape. Examples of this type of prior art are U.S. Pat. Nos. 3,957,631; 3,200,945; 3,073,449; 2,717,692; 2,543,898; 1,677,862 and 633,445. In the rotary drum structures disclosed in these patents, elements of unlike characteristics are separated from each other, while elements of like characteristics are deliberately kept together; the task of separating elements of identical physical characteristics is not contemplated in such prior art.
U.S. Pat. No. 3,759,419, on the other hand, does provide a rotary housing for progressively separating individual elements of identical characteristics from a mass of such elements. However, the device of this patent requires the alignment of all the elements in a substantially parallel relationship for feeding, one at a time, to an exit port gained by means of a centrifugal force of a certain amplitude. Steel fibers of the type used in fiber concrete are notoriously prone to cling to one another in random orientation when a large number thereof are placed in close proximity, such as the contents of the common forty-pound box of such fibers referred to above, and prior to the invention of the apparatus disclosed herein, only manual separation of the fibers has proved effective, if not economical.
Another prior art device utilizing a rotary drum to dispense a plurality of identical articles is disclosed in U.S. Pat. No. 2,040,747. In this device, a plurality of identical headed tacks fall into each of a plurality of pockets spaced apart around the periphery of one end of a rotary drum as the latter is rotated and the spaced-apart pockets come, in turn, to a bottom position. As the drum continues to rotate, the plurality of tacks in each such pocket are carried upwardly thereby, still within the confines of the drum, to an upper position at which they fall into a hopper extending into the drum. This hopper feeds the tacks into a chute, with a vertical alignment of the tacks necessarily being accomplished at this point in order to permit the tacks to ride down the vibratory chute and exit from the drum through the end opening therein through which the drum is charged with a supply of tacks, this being the only opening from the interior of the drum. Tacks which do not properly align themselves for an acceptance by the vibratory chute are brushed off and dropped back down to the bottom of the drum to repeat the cycle.
While the device described in the preceding paragraph, as well as the others described above, bears some superficial resemblance to the apparatus of the present invention, it differs materially from that of the present invention in both structure and function. In short, the device described in the preceding paragraph, as well as the others previously referred to, cannot perform the function or produce the results of that of the present invention.